Messier 108 or M108 (also designated NGC 3556) is a spiral galaxy in the constellation Ursa Major. It has an apparent visual magnitude of 10 and its angular diameter is 8x1 arc-minutes. M108 lies at an estimated distance of 45 million light years. The Equinox 2000 coordinates are RA= 11h 11.5m, Dec= +55° 40´ which makes M108 best seen during the spring. The Messier Spring Star Chart shows the position of all Messier objects visible during that season.
The image above shows the uncropped view of galaxy M108 and planetary nebula M97 through the Takahashi E-180 Astrograph (North is up). A 3x enlargement of this image centered on M108 appears to the right.
Messier's Description of M108
Méchain in his letter to Bernoulli, May 6, 1783)
`Page 265 No. 97 [M97]. A nebula near Beta in the Great Bear. Mr. Messier mentions, when indicating its position, two others, which I also have discovered and of which one is close to this one [M108], the other is situated close to Gamma in the Great Bear [M109], but I could not yet determine their positions.' (from the description of M97)
`Nebula near [M97 and Beta UMa], [position] yet to be determined.'
Messier added a position by hand which Owen Gingerich identified in 1953 as NGC 3556, and is now called M108)
- Object: M108
- Other Names: NGC 3556
- Object Type: spiral galaxy
- Object Data: Apparent Magnitude = 10, Angular Size = 8x1 arc-minutes
- Object Position (Equinox 2000): RA= 11h 11.5m, Dec= +55° 40´, Constellation = Ursa Major
- Date/Time: 2011 Mar 29 at 06:46 UTC
- Location: Bifrost Astronomical Observatory, Portal, AZ
- Mount: Astro-Physics 1200GTO
- Telescope: Takahashi Epsilon 180 Hyperbolic Astrograph
- Camera: Canon EOS 550D (Rebel T2i) (modified with a Baader UV/IR filter)
- Field of View: 1.70° x 2.56° at 1.7 arc-sec/pixel (web version: 10.0 arc-sec/pixel)
- Exposure: 4 x 300s, f/2.8, ISO 800
- File Name: M97M108-01w.jpg
- Processing (Adobe Camera Raw): Graduated Filter, Vignetting Correction, Noise Reduction, White Balance, Curves
- Processing (Photoshop CS5): Average Images, Curves, Noise Reduction
- Original Image Size: 3454 × 5179 pixels (17.9 MP); 11.5" x 17.3" @ 300 dpi
- Rights: Copyright 2011 by Fred Espenak. All Rights Reserved. See: Image Licensing.